The present invention relates to a control system of an electronic exchange, more particularly relates to a terminal equipment for controlling common channel signals and a system of the same in a telephone exchange utilizing said common channel signals, wherein a plurality of said common signalling channels are time divisionally controlled, receiving signals are sent from the terminal equipment to a central processing unit and sending signals are sent from the central processing unit via the terminal equipment to the common signalling channels.
In order to serve the increased quantitative and qualitative demands in the field of communications of present day society, common control type electronic exchanges utilizing electronic devices are being developed in recent years in place of the conventional mechanical control type exchange. The electronic exchange carries out not only high speed switching of a plurality of telephone channels but also provides new services such as abbreviated dialing, call waiting and subscriber dialing for international calling. Further, it provides exchange functions in a total (or integrated, overall) communication network including image or picture communications, data communications and composite picture and data communications, so that the prospect for its future is very promising.
Various methods for the electronic exchange have been proposed. In the present invention, mechanical switches such as crossbar switches are mainly used on the speech channels, and the exchange device is controlled by a stored program control system in accordance with a time division (or sharing) multi-system. Further, in the present invention, a common channel signalling system, for example, No. 6 signalling system recommended by CCITT (Comite Conseltatif International Telegraphique et Telephonique; International Telegraph and Telephone Consultative Committee) is adopted.
First, a common channel signalling system will be briefly explained. This system uses a high speed data transmission technique wherein supervisory telephone signals (on-hook and off-hook of a telephone) and dial pulse signals are transmitted through a single specific channel at a very high speed. In this common channel signalling system, signals of plural speech circuits are simultaneously transmitted through a single common signalling channel which is greatly different from the conventional signalling system wherein telephone signals are transmitted through speech circuits. For example, data of 2,400 bits/sec are transmitted through a common signalling channel using a four-phase differential phase modulation. In this transmitting system one signal unit consists of 20 data bits and 8 check bits for detecting errors by a cyclic code. That is, one signal unit is composed of 28 bits, and one block is composed of 11 signal units. An acknowledgement signal unit (Acu) is inserted every 12 signal units. Different from the telephone signals, this acknowledgement signal unit (Acu) is a special signal unit which has acknowledgement indicators indicating whether the received 11 signal units are right or wrong, a block number sent from the own station and a block number received from the distant station. When the distant station is informed by this acknowledgement indicator that a wrong signal was received, said signal unit is retransmitted. Further, when there is no telephone signal to be sent, a synchronization signal unit (Syu) is sent as a blank signal. Even when the synchronization signal unit (Syu) is received wrong, it is not retransmitted.
The sending and receiving processes of the abovementioned common channel signals are shared by both the common signal controller and the central processing unit.
In the electronic switching system and the signalling terminal according to the conventional technique, when a plurality of common signalling channels are controlled, the signal process and channel control operations are all entrusted to the central processing unit. Consequently, the load of the central processing unit, that is, the amount of processing thereof excessively increases. Further, in the prior art, a terminal having the same function is provided for each of the common signalling channels, and when there are many common signalling channels the hardware circuit elements become tedious, bulky and expensive.
There have been known many electronic exchanges including U.S. Pat. Nos. 3,524,946, 3,558,827, 3,598,914, 3,649,759 and 3,760,364. However, U.S. Pat. No. 3,524,946 to Pinet et al relates to a time division PCM Telephone Exchange, and in particular relates to a register connected to a central computer in an electronic exchange, and has no concern with a common signal control system in which signals in a plurality of channels are commonly transmitted through an separate data link. Therefore, said patent is alleged to relate to a completely different type of exchange from that of the present invention. U.S. Pat. No. 3,558,827 to Lucas et al proposes a new signalling system between a master station and a slave station. In contrast, the present invention as claimed relates to the particular common signal controller for the particular common channel signalling system (such as the No. 6 system recommended by CCITT). Therefore, present invention is believed patentably distinct from Lucas. U.S. Pat. No. 3,598,914 to Synnott does disclose a common signal controller. Synnott's signalling terminal does not operate on a time division basis, as does the one claimed. U.S. Pat. No. 3,649,759 to Buzzard et al relates to a time divisional MODEM for data transmission, but is not concerned at all with common signal controller. Finally, U.S. Pat. No. 3,760,364 to Yamauchi et al shows only a signalling terminal of the class set forth in the prior art FIG. 1 representation of the instant application.